adding a check for if the first arg is an image - annoying if it overwrites

your files if you put in the wrong params.

samples/cpp/imagelist_creator.cpp

@@ -2,6 +2,7 @@
  */
 
 #include "opencv2/core/core.hpp"
+#include "opencv2/highgui/highgui.hpp"
 #include <string>
 #include <iostream>
 
@@ -28,6 +29,13 @@ int main(int ac, char** av)
 
   string outputname = av[1];
 
+  Mat m = imread(outputname); //check if the output is an image - prevent overwrites!
+  if(!m.empty()){
+    std::cerr << "fail! Please specify an output file, don't want to overwrite you images!" << endl;
+    help(av);
+    return 1;
+  }
+
   FileStorage fs(outputname, FileStorage::WRITE);
   fs << "images" << "[";
   for(int i = 2; i < ac; i++){